This invention relates to permanently attachable hydraulic hose couplings and more particularly to a crimp type coupling particularly suited for high pressure, multiple wire ply hoses.
The high pressure hose coupling field has received much attention in the past but currently is even more emphasized in the need for higher pressure requirements in large size hoses. In particular it is desirable to be able to obtain a reliable junction between the hose and coupling in a satisfactory manner and to be able to achieve such connection in a field environment which will duplicate that type of connection which might be made in a factory assembly. Still further it is desired to make such a connection in which no special preparation is required upon the hose such as skiving the outer cover or core tube.
Two types of hose couplings are currently in commercial use in the high pressure environment of six spiral wire reinforced hose. One of these is described for example in U.S. Pat. No. 3,325,194. In this example, the outer cover of the hose must be removed or skived in order to achieve a suitable connection. In this arrangement a collet-type grip is achieved directly on the wire reinforcement when an outer sleeve is axially forced over axial split collet fingers which include internal gripping grooves therein. This type of coupling is reusable but includes the disadvantages of difficult to manufacture components and a difficult to assemble structure wherein separable components must be provisionally placed on a hose end in a proper orientation and then pressed into engagement with one another. The chief drawback however, is the requirement for skiving the cover of the hose.
Skiving is conventionally performed as an abrading process by a grinding wheel or the like where the hose must be supported and rotated in relation to the rotating wheel as well as being moved relative thereto to effect the proper depth of removal of material. Skiving is a difficult process, best performed in a factory environment where close control can be maintained. In the field, inconsistent results often result, for example, where the cover is unevenly removed or even worse when the reinforcement is damaged. These effects result in inconsistent hose joints, which are especially noticeable in high pressure applications where such deviation cannot be tolerated. Skiving is a difficult, dirty, costly and inconsistent process but has been found to be necessary in current practice to achieve high pressure joints in the larger size hoses.
Another example of current practice is described in U.S. Pat. No. 3,347,571. Here, in order to achieve a satisfactory grip upon the hose, both the outer cover and the core tube of the hose are skived so that a direct grip on the reinforcement structure can be made by the crimped shell and nipple of the coupling. Skiving the core tube is even more difficult than skiving the cover and even less control can be exercised over the process where damage to the reinforcement or removal of insufficient amounts cannot be readily viewed.
When a hose structure is skived, exposing the reinforcement, it is very common to have individual wire strands unwind from the hose structure. These strands are extremely stiff and make assembly of the hose joint prior to crimping, very difficult.
Skiving then, is a process which has been developed in an attempt to achieve high performance for critical coupling applications. There are prior art couplings in which high performance is attempted to be achieved in no-skive arrangements where direct engagement is made with the reinforcement structure of the hose through the retained cover member. One example of this is U.S. Pat. No. 3,367,683 wherein a sturdy clamp structure is employed to drive gripping teeth into engagement with the reinforcement. This structure is costly and unwieldy and can be subject to inconsistent results, dependent upon the skill of the assembler and the proper assembly of the individual components.
Another form of prior art device is shown in U.S. Pat. No. 4,150,466 wherein a particular form of barb is utilized in order to achieve penetration of the hose cover and engagement with the reinforcement. A plurality of sharp penetrating barbs is described, with penetration substantially into the reinforcement structure. This disrupts the integrity of the reinforcement and may produce attendant possible damage to the structure. The grip is achieved with a pointed, relatively small profile, distributed structure, which is of a difficult to manufacture, pyramid shape.
Another form of no-skive coupling which avoids penetration of gripping teeth into the reinforcement structure is shown in U.S. Pat. No. 4,366,841. In this type of coupling in which the grip is also achieved by crimping the collar of the coupling, the gripping teeth are designed to accommodate the high crimp forces by bending upon engagement with the wire reinforcement. These gripping teeth are specially shaped for this purpose and are relatively slender in profile.